/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.druid.segment.data;

import com.google.common.primitives.Ints;
import org.apache.druid.java.util.common.io.Closer;

import java.io.Closeable;
import java.io.IOException;
import java.nio.ByteBuffer;

public final class CompressedVariableSizedBlobColumn implements Closeable
{
  private final int numElements;
  private final CompressedLongsReader compressedOffsets;
  private final CompressedBlockReader compressedBlocks;
  private final Closer closer;

  public CompressedVariableSizedBlobColumn(
      int numElements,
      CompressedLongsReader offsetsReader,
      CompressedBlockReader blockReader
  )
  {
    this.numElements = numElements;
    this.compressedOffsets = offsetsReader;
    this.compressedBlocks = blockReader;
    this.closer = Closer.create();
    closer.register(compressedOffsets);
    closer.register(compressedBlocks);
  }

  @SuppressWarnings("unused")
  public int size()
  {
    return numElements;
  }

  public ByteBuffer get(int index)
  {
    final long startOffset;
    final long endOffset;

    if (index == 0) {
      startOffset = 0;
      endOffset = compressedOffsets.get(0);
    } else {
      startOffset = compressedOffsets.get(index - 1);
      endOffset = compressedOffsets.get(index);
    }
    final int size = Ints.checkedCast(endOffset - startOffset);
    return compressedBlocks.getRange(startOffset, size);
  }

  @Override
  public void close() throws IOException
  {
    closer.close();
  }
}
